Thiazolinoazetidinone derivative

A thiazolinoazetidinone derivative represented by the formula ##STR16## wherein R.sup.1 is selected from the group consisting of phenyl, substituted phenyl, methyl, substituted methyl and ##STR17## group, R.sup.3 being one of phenyl and substituted phenyl, and R.sup.2 being one of a hydrogen atom and a carboxylic acid protective group,

• wherein substituents of the substituted phenyl are selected from the group consisting of halogen atoms, straight-chain or branched-chain C.sub.1-4 lower alkyl groups, straight-chain or branched-chain C.sub.1-4 lower alkoxy groups, straight-chain or branched-chain C.sub.1-4 alkylthio groups, amino group, amino groups having one to two straight-chain or branched-chain C.sub.1-4 lower alkyl groups as substituent(s), hydroxy group, protected hydroxy group, nitro group, cyano group, phenyl group ##STR18## group (wherein R.sup.5 is a straight-chain or branched-chain C.sub.1-4 lower alkyl group), and ##STR19## group (wherein R.sup.5 is as defined above);
• and said substituted methyl is selected from the group consisting of --CH.sub.2 Cl, --CHCl.sub.2, --CCl.sub.3, --CH.sub.2 Br, --CHBr.sub.2, --CBr.sub.3, --CH.sub.2 F, --CHF.sub.2, --CF.sub.3, --CHXR.sup.3 group (wherein X is a hydrogen atom, a halogen atom, hydroxyl group, protected hydroxyl group, acetoxy group, amino group or protected amino group, and R.sup.3 is as defined above). ##STR20## group, --CY.sub.2 R.sup.3 group (wherein Y is a halogen atom and R.sup.3 is as defined above), and --CH.sub.2 OR.sup.3 group (wherein R.sup.3 is as defined above),